The present invention relates to the complete rehabilitation of buried pipelines, such as sewer lines, drainage lines, water mains, and the like. More particularly, the present invention relates to the complete rehabilitation over long distances of very large diameter curved and buried pipelines. According to the method of the present invention, such rehabilitation is achieved without digging up a substantial portion of the buried pipeline.
In the past it was common to use buried cement, iron, masonry, or clay conduits to convey sewage, drainage, and other materials. Of course these systems decay over a period of years due to deterioration or corrosion, root action, and ground movement. The conventional method of repair is to excavate the faulty buried pipeline and replace such portions as are necessary. The disadvantages of such excavations are the disruptions of neighborhoods, roads, and streets caused by trenches of from 6 to 30 feet in depth. More particularly, the sewer service, or other service, is completely disrupted unless expensive bypasses are constructed.
It has been suggested heretofore, for example, in U.S. Pat. No. 3,950,461, that the disadvantages of excavation could be overcome by the insertion of a flexible continuous liner into the pipeline from a convenient access point. In the prior art method, a continuous liner is pushed through the length of the pipeline to another access point, perhaps spanning distances as long as 1500 feet. The annular space between the liner and the inner surface of the buried pipeline would be filled with cements, e.g., U.S. Pat. No, 4,170,248.
Unfortunately, in many applications the liner for the underground pipes has very thick walls and is difficult to bend. To insert a stiff liner, it may be necessary to greatly elongate the excavation so that the stiff liner may be gradually deformed into a curve of large radius. But this is again a disadvantageous disruption of traffic at great cost. The use of bending devices as taught in U.S. Pat. No. 4,504,171 for sliplining by continuous plastic liners is not practical on pipes of large diameter and substantial wall thicknesses.
The present invention solves the problem of rehabilitating large diameter buried pipelines by discarding the prior art's flexible continuous or semicontinuous pipeliners and adopting a segmented pipeline liner. A segmented pipeline liner requires joints between its segments. The joints used in the process of the present invention are specifically designed for ease of entry into the buried pipeline over long distances, and can be specifically designed (i.e., articulated) for lining curved pipelines having radii of curvature even less than 50 feet.
Surprisingly, it has been found that these properties are attainable with jointed high density polyethylene liner pipe section produced by the helical winding of polyethylene strips and reinforcing members on a rotating mandrel.